The present invention relates to a construction for installing the stepping motor of a floppy disk drive unit to a frame, and more particularly, to a construction for enabling the stepping motor to be installed with ease and high accuracy.
A conventional construction for installing the stepping motor of a floppy disk drive unit is shown in FIG. 1, in which reference numerals 10 and 16 denote a carriage and a stepping motor, respectively. Pulley 14 is attached to the rotating shaft of stepping motor 16. Steel belt 12 is wound around pulley 14, and the ends of steel belt 12 are secured to carriage 10. Securing portion 18 projects from each side of stepping motor 16. An elongated hole, which extends in a perpendicular direction to the rotating shaft, is provided in each securing portion 18. Setscrew 22 is inserted into elongated hole 22 and is threadedly fitted into a tapped hole formed in the frame.
In the floppy disk drive unit described above, stepping motor 16 must be moved such that carriage 10 is accurately positioned with reference to the predetermined position of the disk, so as to ensure compatibility among different disks. Conventionally, this positional adjustment has been made in the following manner. First, stepping motor 16 is temporarily secured to the frame of the floppy disk drive unit, in the state where setscrew 20 is not fastened. Next, carriage 10 is coupled to stepping motor 16 by use of pulley 14 and steel belt 12. Thereafter, stepping motor 16 is excited such that the rotational angle of the rotating shaft corresponds to the angle determined by the reference position of a disk used for position adjustment, thereby magnetically fixing the rotating shaft at the position determined by the reference rotational angle. Under this condition, the position of a magnetic head provided on carriage 10 is adjusted to the reference position of the disk used for position adjustment. More specifically, stepping motor 16 is moved in the direction indicated by arrow 24 in FIG. 1, i.e., parallel to steel belt 12, while simultaneously permitting the magnetic head to read the data stored in the disk. At this time, carriage 10 moves together with stepping motor 16, so that the magnetic head moves on the disk. After the magnetic head is moved to the position corresponding to the reference position of the disk, setscrew 20 is fastened, thus completing the position adjustment between stepping motor 16 and carriage 10.
When fastening setscrew 20, torque may be applied to stepping motor 16, so that stepping motor 16 may rotate in a horizontal plane. When this happens, however, steel belt 12 is twisted slightly, so that the accuracy of the adjustment is not significantly affected. For this reason, conventional stepping motor 16 is not provided with a guide member for guiding the movement of stepping motor 16 in the direction of arrow 24.
With the recent miniaturization in floppy disk drive units, smaller stepping motors have been developed. FIG. 2 illustrates a conventional construction for installing such small stepping motors. Referring to FIG. 2, stepping motor 38 is disk-shaped. Securing-portion 40 of stepping motor 38 is located in a plane perpendicular to the rotating shaft of motor 38. Pulley 36 is attached to the end of the rotating shaft. Steel belt 32 is wound around pulley 36, and the ends of steel belt 32 are secured to the side wall of carriage 30. An arcuately elongated hole is provided in each securing portion 40 such that the center of the arcs is located at the rotating shaft. Setscrew 46 is inserted in elongated hole 42 and is threadedly fitted into a tapped hole formed in frame 34. Circular projection 39 is formed at the foot of the rotating shaft of stepping motor 38. Stepping motor 38 is positioned by fitting projection 39 into a hole formed in frame 34.
When installing the small stepping motor mentioned above, adjustment is made in the following fashion. First, stepping motor 38 is temporarily secured to the frame of the floppy disk drive unit, in the state where setscrew 46 is not fastened. Next, carriage 30 is coupled to stepping motor 38 by use of pulley 36 and steel belt 22. Thereafter, stepping motor 38 is excited such that the rotational angle of the rotating shaft corresponds to the angle determined by the reference position of a disk used for position adjustment, thereby magnetically fixing the rotating shaft at the position determined by the reference rotational angle. Under this condition, the position of a magnetic head provided for carriage 30 is adjusted to the reference position of the disk used for position adjustment. More specifically, stepping motor 38 is rotated in the direction indicated by arrow 48 in FIG. 2, while simultaneously permitting the magnetic head to read the data stored in the disk. With rotation of stepping motor 38, carriage 30 moves linearly, so that the magnetic head provided for carriage 30 also moves on the disk. After the magnetic head is moved to the position corresponding to the reference position of the disk, setscrew 46 is fastened, thus completing the position adjustment between stepping motor 38 and carriage 30.
When fastening setscrews 46, however, torque may be applied to the stepping motor, due to the friction between the screws and the securing portions, so that stepping motor 38 is apt to be shifted from the reference position. Therefore, stepping motor 38 cannot be always adjusted with high accuracy when is installed. If the rotating shaft of stepping motor 38 is moved 1.0.degree. , carriage 30 will move by the distance corresponding to one pitch of the tracks on the floppy disk. As can be seen from this, the adjustment is significantly affected even if stepping motor 38 is shifted only slightly from the reference position.
One object of the present invention is to provide a stepping motor-installing construction which enables adjustment to be made with high accuracy, even when a small stepping motor is installed.
Another object of the present invention is to provide a stepping motor installing construction which enables a stepping motor to be installed with ease and high accuracy, even by an unskilled person.